Process for acylating functional groups bearing active hydrogen with isopropenyl esters of long-chain fatty acids

ABSTRACT

Materials containing an active hydrogen are acylated quickly and easily at low temperatures by reacting them with an in situ acylating agent formed by the reaction of a strong oxy acid and an isopropenyl ester containing from about 9 to 22 carbon atoms. When used on fibrous cellulosic materials, the process imparts to the treated material a water repellency that is durable to dry cleaning and to aqueous laundering with neutral detergents. The process does not significantly alter the strength, color, appearance, hand or fibrous form of the cellulosic material.

United States Patent 1 Mariner et al.

[ Apr. 29, 1975 [75] Inventors: William N. Mariner; Samuel Serota,

both of Philadelphia; Gerhard Maerker, Oreland, all of Pa.

[73] Assignee: The United States of America as represented by the Secretary of Agriculture, Washington, DC.

22 Filed: Sept. 21, 1972 211 App]. NO.2 290,933

[52] U.S. Cl. 260/212; 8/121; 260/224 [51] Int. Cl C081) 3/02 [58] Field of Search 260/212, 691, 224; 8/121, 8/120 [56] References Cited UNlTED STATES PATENTS 3,215,488 11/1965 Suiter 8/116.4

3,299,025 1/1967 Leavitt et a1 260/691 3,432,252 3/1969 McKelvey et a1 8/120 3,478,016 11/1969 Rowley 260/212 3,493,319 2/1970 Berni et a1. 8/120 3.6l7,201 11/1971 Berni et a1. 8/120 Primary ExaminerRona1d W. Griffin Attorney, Agent, or Firm-M. Howard Silverstein; Max D. Hensley; William E. Scott [57] ABSTRACT Materials containing an active hydrogen are acylated quickly and easily at low temperatures by reacting them with an in situ acylating agent formed by the reaction of a strong oxy acid and an isopropenyl ester containing from about 9 to 22 carbon atoms. When used on fibrous cellulosic materials, the process imparts to the treated material a water repellency that is durable to dry cleaning and to aqueous laundering with neutral detergents. The process does not significantly alter the strength, color, appearance, hand or fibrous form of the cellulosic material.

11 Claims, No Drawings PROCESS FOR ACYLATING FUNCTIONAL GROUPS BEARING ACTIVE HYDROGEN WITH ISOPROPENYL ESTERS OFLONG-CHAIN FATTY ACIDS A non-exclusive irrevocable, royalty-free license in the invention herein described, for all Goverment purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Goverment of the United States of America.

This invention relates toa-facile acylation of hydrogen-bearing compounds under exceptionally mild conditions and more particularly to-the acylation of functional groups bearing active hydrogen and still more particularly to the production of acylated materials with enhanced properties,- such as water repellency, without altering significantly the desirable properties of the materials.

Esterification of fibrous cellulosic material with longchain fatty acids and trifluoroacetic anhydride in benzene is known in the prior art (US. Pat. No. 3,493,3l9). ln such a process, there is a competitive reaction between the trifluoroacetic anhydride (impellor agent) and cellulose which can proceed too rapidly, affording a trifluoroacetylated product instead of a long-chain fatty ester derivative. ln the esterification of fibrous cellulosic materials which long-chain fatty alkanoicandalkenoic halides, well known to the prior art (U-. S =-.-l?at.; No. 3,432,252), bases such as pyridine, triethyl-amine andsodium bicarbonate must be used to neutralize free acid. However, despite this need for neutralization and for numerous chemical washings, the halogen acid formed frequently disintegrates the fibrous cellulosic material. In other processes, well known to the prior art, the chemicals used to treat the fibrous cellulosic. material .do not form a covalently bonded product. Since no formation of a chemical derivative of the fibrous cellulosicmaterial occurs, only a physical layer covers the fabric; consequently the Water repellency of the product is not durable to dry cleaning and to laundering with neutral detergents and is a serious drawback to practical commercial applications of the treated textiles. Another disadvantage to many of the presently available processes is the tendency of thetreated fabric to blemish upon mild abrasion..

An object of this invention is to provide a new and improved acylation process for the esterification of hydroxy group-containing cellulosic textile fibers, fibrous paper, paper products, wood and wood products, without destroying the fibrousnature of these materials.

Another object is to provide a process for modifying the the properties of fibrous cellulosic materials in order to impart or enhance water repellency to such diverse cellulosic materials as paper cartons for milk and other beverages, cotton raincoats, bathing suits, paper bags, and canvas for sneakers. Paper cartons and canvas made waterrepellent by a process that does not affect their biodegradability or their porosity would be especially advantageous.

A further object is to provide long-chain alkanoic and alkenoic esters 6r) fibrous cellulosic materials wherein the product resulting from the acylation is durable to dry cleaning and to aqueous laundering with neutral detergents. I

Still another object of this invention is the lowtemperature and rapid production'of acyl derivatives of any compound or materials containing functional groups with an active hydrogen. Such acyl derivatives often drastically change the properties of the original compounds. For example, lecithin, whose stearoyl derivative acts as an emulsion and foam stabilizer; butyl alcohols, whose stearoylated derivatives are used as plasticizers and as lubricants for synthetic textile spinning and for rolling of aluminum sheets and whose myristoylated derivatives are used as cosmetic bases; amines, whose derivatives, fatty acid amides, are used as foam stabilizers, as slip and antiblock agents for polyethylene, as paint thickeners, as dye solubilizers for wax formulations, as plasticizers, and as lubricant additives, and various amide-type compounds, such as wool, whose partially acylated derivative exhibits water repellent properties.

We have discovered an improved acylation process for the production of alkanoyl and alkenoyl esters of fibrous cellulosic materials whereby the treated mate rial retains its fiber. structure and is rendered water repellent even at a low degree of substitution. This improved acylation process, which requires only a slight modification of existing industrial equipment, imparts to the treated material a water repellency that is durable to dry cleaning and to aqueous laundering with neutral detergents and does not significantly alter the strength, color, appearance, hand or fibrous form of the treated cellulosic material. In addition, in the improved process of this invention, hydrogen directly attached to atoms such as nitrogen, sulfur, and oxygen is replaced with a longchain fatty acyl radical.

' In general, in accordance with the present invention, a material containing an active hydrogen is acylated by reacting it with an in situ acylating agent formed by the reaction of a strong oxy acid and an isopropenyl ester containingfrom about 9 to 22 carbon atoms. The usual and convenient procedure is to dissolve the isopropenyl ester in a solvent having a low dielectric constant such as methylene chloride, chloroform, carbon tetrachloride, nitrobenzene or benzene and then add the strong oxy acid to the solution to form the acylating agent. The material to be acylated is then treated with the solution of the acylating agent. The acylation may be done at a temperature ranging from just above the freezing point of the solution of acylating agent to just below that temperature at which an undesirable amount of decomposition of the material to be acylated occurs. However, reaction temperatures from about 0 to 30C are preferred. The process is characterized by an unusually short reaction time of the acylating agent with the material to be acylated, and by the simplicity, especially in the instance of the acylation of cellulosic material, of washing the final product.

' Another important feature of this invention is that the by-products of the process, acetone and free acid,

and the like; partial esters of cellulose such as partially acety ated cellulose, beta-propiolactone-reacted cellulose and the like; partial ethers of cellulose such as partially cyanoethylated, partially carboxymethylated, partially aminoethylated and the like; natural and synthetic fibers such as wool, polyester and blends of these fibers such as cotton with polyester and the like; methyl and t-butyl alcohols, t-butyl-amine, p-toluene sulphonamide, lauryl mercaptan and similar chemicals in which the hydrogen directly attached to a functional group maintains some degree of lability. In general, the cellulosic textile fibers in the form of free fibers, slivers, yarns, or fabrics, including the natural fibers and partial ethers or partial esters thereof, which retain their cellulosic textile properties are preferred starting materials. The cellulose textile fibers in the form of spun textiles such as yarns, threads or cloths, are particularly suitable starting materials. ln this invention, the choice of solvent is critical, in that only aprotic solvents of low dielectric constant may be used to generate the active acylating agent.

The novel acylating agents of this invention are most easily prepared by reacting the desired isopropenyl ester in methylene chloride solution with a strong oxy acid. The oxy acid must be an exceptionally strong acid such as methanesulfonic, trifluoromethanesulfonic and sulfur trioxide. None of the acids usually considered to be strong such as trifluoroacetic, sulfuric and phosphoric are operative in the process of this invention. Other solvents, such as benzene and carbon tetrachloride may be used. Acetone is liberated in the formation of the acylating agent and the resulting solution is used for the purposes of this invention.

lsopropenyl esters of any long-chain fatty acid, saturated or unsaturated, wherein the acyl radical contains from 9 to 22 carbon atoms can be used in the present process. lsopropenyl esters that can be employed include lauric, oleic, stearic, linoleic, linolenic, palmitic and the like, derivatives of such esters including 2- buty1-2-heptyl decanoate ester and ester mixtures such as isopropenyl tallowate, which is largely isopropenyl oleate with lesser amounts of the palmitic and stearic esters..

The strong and soluble oxy acids that can be employed with the isopropenyl esters to make the active acylating agent include methanesulfonic acid, trifluoromethanesulfonic acid, para-toluenesulfonic acid, sulfur trioxide and the like strong and soluble acid oxides.

When the material to be acylated is a chemical compound, the process usually requires that the compound be in solution. Consequently, the acylating agent must be dissolved in a solvent that will also dissolve the compound to be acylated. Occasionally, a solvent that will dissolve the compound cannot be used to prepare the acylating agent. When this occurs, the acylating agent can be prepared using methtylene chloride and the methylene chloride solution of the acylating agent added to a solvent in which the compound is soluble. Alternatively, the methylene chloride can be removed from the acylating agent by evaporation or other means and the residual acylating agent dissolved in the desired solvent.

The reaction solution is preferably prepared using a mole ratio of cellulose (anhydroglucose units, AGU) to isopropenyl fatty ester to strong oxy acid of about 2:2: 1, respectively. The long-chain isopropenyl fatty ester is first dissolved in solvent and the'strong oxy acid is then added. After a short waiting period, the desired product is formed. That these products are powerful acylating agents is evidenced by the rapid esterification of the hydroxyl function of filter paper, a fibrous cellulosic material, at room temperature. Simply dipping the filter paper into a methylene chloride solution of any of the acylating agents of this invention for less than 1 minute followed by washing with warm methylene chloride alone affords permanently waterproof paper. In carrying out this improved acylation process on cellulosic material, predrying of the fibrous cellulosic material is not recommended because it may seriously curtail the rate of acylation.

An unexpected feature of this invention is that the process can be used to make dyed fabrics water repellent without impairing the dye. In addition, this improved acylation process does not alter significantly the strength, appearance, hand or fibrous form of the finished fabrics.

The invention is illustrated in the following examples:

EXAMPLE 1 2.12 ml. (72.1 mmol) of methanesulfonic acid was added to 200 ml. of a methylene chloride solution containing 20.6 g. (63.9 mmol) of isopropenyl stearate and the mixture allowed to react 5 minutes to form an acylating agent. A sheet offilter paper, 1.75 g. 10.7 mmol AGU) (W & R Balston, Ltd., No. 42 filter paper, maximum ash per circle 0.00017 g.)], was then completely immersed in this acylating agent for one minute, washed with methylene chloride, air dried and equilibrated. On testing the treated filter paper was found to be completely water repellent; water globules collected on its surface and no wetting of the paper occurred.

EXAMPLE 2 2.0 ml. (35 mmol) of methanesulfonic acid was added to 100 ml. of a methylene chloride solution containing 1 1 .0 g. (35 mmol) of isopropenyl tallowate and the mixture allowed to react 5 minutes to form an acylating agent. A 2.99 g. (18.4 mmol AGU) swatch of desized and bleached X 80 cotton fabric was immersed in the acylating agent and agitated occasionally over a 15 minute period. The fabriewas removed, rinsed in methylene chloride, air dried, and equilibrated. On testing, water collected in droplets on its surface. Vigorous shaking of the fabric completely removed the water and the fabric was dry to the touch immediateley. No water penetrated the fabric.

EXAMPLE 3 An acylating agent was prepared by adding 1.0 ml (4.2 mmol) of sulfur trioxide to 15 ml. of methylene chloride containing 1.33 g. (4.13 mmol) of isopropenyl stearate at 0C. A swatch of 80 X 80 cotton fabric (.7663 g., 4.1 mmol AGU) was immersed beneath the surface of the cooled acylating agent and shaken occasionally over a 15 minute period. The fabric was washed twice with acetone, twice with water, and twice again with acetone. After drying for 0.5 hr. with forced air and then cquilibrating, the partially acylated cotton fabric was found to be water repellent, as exhibited by water globules forming on its surface and remaining there for a prolonged period of time without wetting the underside of the fabric. There was no significant alteration in the tear strength, color, appearance, hand or fibrous form of the treated fabric.

EXAMPLE 4 A solution of isopropenyl stearate (120.0 g., 0.38 mol) in methylene chloride (700 ml.) was chilled to 12C and stirred while liquid sulfur trioxide (8.4 ml., 0.9 mol) was added dropwise and the solution allowed to warm to room temperature (about 25C) over a minute period. The following cellulosic materials were then immersed in the acylating agent formed above:

a. a Kraft paper bag (4.57 g., 26.8 mmol AGU);

b. the following dyed cotton and dyed cotton blend fabrics:

(b-l) yellow cotton twill (5.67 g., 35.0 mmol .AGU);

(b-2) green cotton rib knit (4.37 g., 27.0 mmol AGU);

(b-3) being cotton polyester twill (4.93 g., 15.2 mmol AGU): i

c. 80 X 80 cotton print cloth which had been desized,

scoured and bleached (1.47 g., 9.09 mmol AGU).

The fabrics were treated for minutes and the Kraft paper bag for 1.5 hr. at about C. All of the materials were then washed with warm chloroform. The cellulosic materials were then vacuum dried, air equilibrated, and tested for water repellency. The acylated Kraft paper bag held water to a depth of 3 inches without any penetration of water to the outer surface of the bag. The cotton and cotton blend fabrics were found to be water repellent and retained their hand, strength, appearance, and original color. Furthermore, all the acylated fabrics maintained their water repellency, hand, strength, and color after laundering with a neutral detergent according to the military specificataion Mil-D-43362.

EXAMPLE 5 Methanesulfonic acid (228.0 ml., 3.51 mmol) was added to a solution of isopropenyl stearate (1.14 g., 3.51 mmol) in methylene chloride (3.0 ml) and allowed to react at about 25C. Five minutes later, the solvent was removed under vacuum, leaving a residue of the prepared acylating agent. The residue was dissolved in dry acetone (3ml.) and then triethylamine (490p.1, 3.51 mmol) and the methanol (142 pl, 3.51 mmol) were added and reacted at about 25C. Ten minutes later, the solution was washed with a water/- methylene chloride system. The organic phase was dried with anhydrous magnesium sulfate, filtered, and stripped of solvent. An infared spectrum of the product was identical to an authentic spectrum of methyl stearate. The yield was 42%.

EXAMPLE 6 To a solution of isopropenyl stearate (0.48 g., 1.5 mmol) inmethylene chloride (5.0 ml.), methanesulfonic acid (96 p.l., 1.5 mmol) was added and reacted at about 25C. After 5 minutes, the solvent was removed under vacuum and the residue redissolved in dry acetone (5ml.). A 1.35 g., 8.32 mmol AGU) piece of 80 X 80 cotton print cloth, bleached, scoured, and desized was added and treated for 10 minutes at about 25C. The fabric was removed, washed with methylene chloride, and then air dried. On testing, the fabric was found to be water repellent and to retain its whiteness, hand. and tear resistance. Similar results were obtained by using N-methylpyrrolidone or N, N-dimethylformamide in place of the acetone.

EXAMPLE 7 To a stirred solution of isopropenyl stearate 1.29 g., 3.97 mmol) in methylene chloride solution (4 ml.), methanesulfonic acid (258 a], 3.98 mmol) was added and allowed to react at about 25C for 10 minutes. Dry t-butanol (5ml.) was then added and after reacting for 4 minutes at about 25C, the reaction mixture was washed with excess aqueous sodium bicarbonate solution followed by drying of the organic phase with anhydrous sodium sulfate. Re-crystallization from acetone afforded tbutyl stearate 1.07 g.), mp 295C, identification confirmed by gas-liquid chromotography.

EXAMPLE 8 In order to demonstrate further the utility of this new acylating agent, the following four experiments were run side by side. Four individual 1.0 g. (3.1 mmol) portions of isopropenyl stearate were dissolved in individual portions of methylene chloride (each 10 ml.). Liquid sulfur trioxide (0.14 ml., 3.1 mmol) was added to each of the above solutions and allowed to react for 10 minutes at about 25C to form four individual solutions of acylating agent. One of the following compounds was then added to each solution of acylating and reacted at about 25C.

a. methanol (0.13 ml., 3.1 mmol);

b. lauryl mercaptan (0.73 ml., 3.1 mmol);

c. para-toluenesulfonamide (0.54 g., 3.1 mmol);

- d. tert-butylamine (1.0 ml., 9.3 mmol). After 30 minutes, the solution was washed with water and extracted with methylene chloride. The nonaqueous layer was then dried over magnesium sulfate and filtered. The solvent was removed and the residue dissolved in petroleum ether and column chromatographed on a suitable adsorbent such as Florisil to yield the following products which were identified by their infrared spectra and melting points:

a. methyl stearate, 78% yield;

b. laurylthiolstearate, 55%;

c. Nstearoyl-p-toluenesulfonamide, 83%;

d. N-tert-butylsteara'mide, 52%.

We claim:

1. A process for preparing an acylated derivative of a chemical compound having a hydrogen atom directly attached to an atom selected from the group consisting of nitrogen, sulfur and oxygen, comprising, forming, in situ, an acylating agent by reacting for about 5 to 10 minutes at about 25C an isopropenyl ester containing from about 9 to 22 carbon atoms and a strong oxy acid selected from the group consisting of methanesulfonic acid, sulfur trioxide, trifluoromethanesulfonic acid and p-toluenesulfonic acid, the molar ratio of isopropenyl ester to oxy acid being about 1:1, said reaction being conducted in an organic solvent of low dielectric constant which does not react with the acylating agent and in which both the chemical compound and the acylating agent are soluble, adding to said formed acylating agent a chemical compound having a hydrogen atom directly attached to an atom selected from the group consisting of nitrogen, sulfur and oxygen, the molar ratio of the acylating agent to the chemical compound ranging from about 1:1 to about 1:15; and allowing the acylating agent and the compound to react for from 1 7 to 30 minutes at a temperature of from about to 30C.

2. The process of claim 1 wherein the isopropenyl ester is isopropenyl stearate and the strong oxyacid is sulfur trioxide.

3. The process of claim 2 wherein the chemical compound is methanol.

4. The process of claim 2 wherein the chemical compound is lauryl mercaptan.

5. The process of claim 2 wherein the chemical compound is p-toluenesulfonamide.

6. The process of claim 2 wherein the chemical compound is t-butylamine.

7. The process of claim 1 wherein the isopropenyl ester is isopropenyl stearate and the strong oxy acid is methanesulfonic acid.

8. A process for acylating fibrous cellulosic materials, chemical compounds and other substances which bear a hydrogen atom directly attached to an atom selected from the group consisting of nitrogen, sulfur and oxygen, comprising the steps of:

a. forming an acylating agent by reacting for about 5 to minutes at a temperature of from about 12 to 30C an isopropenyl ester containing from about 9 to 22 carbon atoms and an oxy acid that is soluble in the reaction medium and capable of liberating acetone in the formation of the acylating agent, the molar ratio of isopropenyl ester to oxy acid ranging from about 1:1 to about 2:1, said reaction being conducted in an organic solvent of low dielectric constant which does not react with the acylating agent and in which both the acylating agent and the nonfibrous materials are soluble;

b. combining the acylating agent and the substance to be acylated; and

c. allowing the acylating agent and the substance to be acylated to react for from l to 30 minutes at a temperature of from about 0 to about 30C, the molar ratio of acylating agent to the substance being acylated ranging from about 1:1 to 1:15 when the substance is a chemical compound and from about 1:1 to about :1 when the substance is a fibrous cellulosic material.

9. The process of claim 8 wherein the solvent of low dielectric constant is selected from the group consisting of methylene chloride, chloroform, carbon tetrachloride, nitrobenzene and benzene and the strong oxy acid is selected from the group consisting of methanesulfonic acid, sulfur trioxide, trifluoromethanesulfonic acid and p-toluenesulfonic acid.

10. The process of claim 9 wherein both the acylating agent and the substance to be acylated are in solution when they are combined.

11. The process of claim 9 wherein prior to combining the acylating agent and the substance to be acylated the solvent of low dielectric constant is removed from the acylating agent and the acylating agent is redissolved in a solvent compatible with that in which the substance to be acylated is dissolved. 

1. A process for preparing an acylated derivative of a chemical compound having a hydrogen atom directly attached to an atom selected from the group consisting of nitrogen, sulfur and oxygen, comprising, forming, in situ, an acylating agent by reacting for about 5 to 10 minutes at about 25*C an isopropenyl ester containing from about 9 to 22 carbon atoms and a strong oxy acid selected from the group consisting of methanesulfonic acid, sulfur trioxide, trifluoromethanesulfonic acid and p-toluenesulfonic acid, the molar ratio of isopropenyl ester to oxy acid being about 1:1, said reaction being conducted in an organic solvent of low dielectric constant which does not react with the acylating agent and in which both the chemical compound and the acylating agent are soluble, adding to said formed acylating agent a chemical compound having a hydrogen atom directly attached to an atom selected from the group consisting of nitrogen, sulfur and oxygen, the molar ratio of the acylating agent to the chemical compound ranging from about 1:1 to about 1: 15; and allowing the acylating agent and the compound to react for from 1 to 30 minutes at a temperature of from about 0* to 30*C.
 2. The process of claim 1 wherein the isopropenyl ester is isopropenyl stearate and the strong oxy acid is sulfur trioxide.
 3. The process of claim 2 wherein the chemical compound is methanol.
 4. The process of claim 2 wherein the chemical compound is lauryl mercaptan.
 5. The process of claim 2 wherein the chemical compound is p-toluenesulfonamide.
 6. The process of claim 2 wherein the chemical compound is t-butylamine.
 7. The process of claim 1 wherein the isopropenyl ester is isopropenyl stearate and the strong oxy acid is methanesulfonic acid.
 8. A PROCESS FOR ACYLATING FIBROUS CELLULOSIC MATERIALS, CHEMICAL COMPOUNDS AND OTHER SUBSTANCES WHICH BEAR A HYDROGEN ATOM DIRECTLY ATTACHED TO AN ATOM SELECTED FROM THE GROUP CONSISTING OF NITROGEN, SULFUR AND OXYGEN, COMPRISING THE STEPS OF: A. FORMING AN ACYLATING AGENT BY REACTING FOR ABOUT 5 TO 10 MINUTES AT A TEMPERATURE OF FROM ABOUT -12* TO 30*C AN ISOPROPENYL ESTER CONTAINING FROM ABOUT 9 TO 22 CARBON ATOMS AND AN OXY ACID THAT IS SOLUBLE IN THE REACTION MEDIUM AND CAPABLE OF LIBERATING ACETONE IN THE FORMATION OF THE ACYLATING AGENT, THE MOLAR RATIO OF ISOPROPENYL ESTER TO OXY ACID RANGING FROM ABOUT 1:1 TO ABOUT 1:1, SAID REACTION BEING CONDUCTED WHICH DOES NOT REACT WITH THE ACYLATDIELECTRIC CONSTANT WHICH DOES NOT REACT WITH THE ACYLATING AGENT AND IN WHICH BOTH THE ACYLATING AGENT AND THE NONFIBROUS MATERIALS ARE SOLUBLE, B. COMBINING THE ACYLATING AGENT AND THE SUBSTANCE TO BE ACYLATED, AND C. ALLOWING THE ACYLATING AGENT AND THE SUBSTANCE TO BE ACYLATED TO REACT FOR FROM 1 TO 30 MINUTES AT A TEMPERATURE OF FROM ABOUT 0* TO ABOUT 30*C, THE MOLAR RATIO OF ACYLATING AGENT TO THE SUBSTANCE BEING ACYLATED RANGING FROM ABOUT 1:1 T 1:15 WHEN THE SUBSTANCE IS A CHEMICAL COMPOUND AND FROM ABOUT 1:1 TO ABOUT 40:1 WHEN THE SUBSTANCE IS A FIBROUS CELLULOSIC MATERIAL.
 9. The process of claim 8 wherein the solvent of low dielectric constant is selected from the group consisting of methylene chloride, chloroform, carbon tetrachloride, nitrobenzene and benzene and the strong oxy acid is selected from the group consisting of methanesulfonic acid, sulfur trioxide, trifluoromethanesulfonic acid and p-toluenesulfonic acid.
 10. The process of claim 9 wherein both the acylating agent and the substance to be acylated are in solution when they are combined.
 11. The process of claim 9 wherein prior to combining the acylating agent and the substance to be acylated the solvent of low dielectric constant is removed from the acylating agent and the acylating agent is redissolved in a solvent compatible with that in which the substance to be acylated is dissolved. 